Determination of Distribution of Fines in a Paper Structure using Fluorescence Microscopy and Image Analysis

• When making paper a sheet is formed by draining a specific amount of dilute water suspension of pulp through a wire-cloth. The procedure is well known but the underlying mechanisms are not fully understood. The different particles such as fines, fibers, retention aids and other additives interact with each other during the process. These interactions are important since they impact the properties of the formed paper. The fibers have different sizes and the finest particle fraction is called fines. The fines used in this study are from bleached kraft pulp and are therefore oxidized to some extent. By labelling the fines with a fluorophore the movements of individual fines can be followed with video-based fluorescence microscopy even if the size of the fines is below the microscopes resolution limit. [1-3] The fluorophores that has been used are N-Methylisatoic anhydride and fluorescein-5-thiosemicarbazide. N-Methylisatoic anhydride reacts directly with hydroxyl groups on the cellulose chain. Fluorescein-5-thiosemicarbazide reacts with groups like aldehydes and ketones in the cellulose chain, so the chain has to be oxidized before the labeling process. These two fluorephores have different absorption and emission wavelengths. [4]The methods for labeling the fibers are easy to perform. The labeled fiber can be seen in the microscope. One problem is that the fibers aggregate, probably due to the method used for labeling. Another problem can be the fading of the flourophores. Both problems will be further investigated. [5]The elevated drying process in the paper machine makes it difficult to understand the mechanisms involved. Within this project the understanding will be built up in many steps. The first step is to study the labeled fibers in water. A model system containing fibers and latex will be used to study the behavior in different environments such as different electrolyte concentration and pH. References[1] Carlsson G., Warszynski P., van Stam J., J. Colloid Interface Sci., 2003, 267, 500-508[2] Carlsson G., van Stam J., Nord. Pulp Pap. Res. J., 2005, 20, 192-199[3] Carlsson G., Järnström L., van Stam J., J. Colloid Interface Sci., 2006, 298, 162-171[4] DeAngelis P. L., Analytical Biochemistry, 2000, 284, 167-169 [5] Rådberg W., Bsc thesis, Karlstad university, 2010

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

fluorescence microscopy

image analysis

cellulose fiber

Chemistry

Kemi

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